In hoists of the type to which the present invention is applicable, the intermediate and top telescopic stages each comprise a piston from which a cylinder extends upwardly to fit over the piston and cylinder of the next higher stage. The bottom stage has a stationary cylinder receiving the lowest intermediate stage. It is preferred to have the lowest intermediate stage be the first to move up and down during working height adjustments. To this end, some of the prior art hoists have an upwardly projecting hollow probe mounted at the bottom of the hoist through which the compressed air passes for raising and lowering the hoist. When the piston of the lowest intermediate stage approaches its lowered position, the probe extends through a passage in the piston and unseats a ball retained in the piston and normally functioning as a check valve to prevent air venting from the higher stages of the hoist. In the past, the probe has been rigid and given a working tolerance of about 0.007 inch with respect to the wall of the piston passage through which it extends to unseat the ball. This tolerance has been considered necessary in view of the normal radial tolerances between the telescopic elements of the hoist. In such prior art hoists, short erratic up and down movements have been experienced when the bottom stage is lowered to the point that the probe is in position to unseat the ball to vent the stages thereabove. The present invention aims to eliminate such erratic movements.